Pressure-regulating valve

ABSTRACT

A pressure-regulating valve having a valve piston (I 0 ) which is subjected to the action of an energy store and which is guided in longitudinally displaceable fashion in a valve housing ( 12 ), which valve housing has ports such as a supply port ( 14 ), a utility port ( 16 ) and a tank port ( 18 ), which ports can be actuated, by way of a control part ( 20 ) which closes with a sealing action, such that, in the case of a fluidic connection from the supply port to the utility port, a pressure reduction function is realized, and in the case of a fluidic connection from the utility port to the tank port, a pressure-limiting function is realized, characterized in that the control part ( 20 ) has a control rod ( 22 ) with two control bodies ( 24, 26 ) held spaced apart from one another, of which control bodies one ( 24 ) controls at least the fluidic connection between supply port ( 14 ) and utility port ( 16 ), and the other control body ( 26 ) controls at least the fluidic connection between utility port ( 16 ) and tank port ( 18 ).

The invention relates to a pressure-regulating valve having a valvepiston which is subjected to the action of an energy store and which isguided in a longitudinally displaceable manner in a valve housing, whichvalve housing has connection points such as a supply connection, autility connection and a tank connection, which connections can beactuated, by means of a control part which closes in a seat-tightmanner, such that, in the case of a fluidic connection from the supplyconnection to the utility connection, a pressure reduction function isrealized, and in the case of a fluidic connection from the utilityconnection to the tank connection, a pressure-limiting function isrealized.

Pressure-regulating valves are frequently used in a hydraulic circuitfor the purpose of converting a variable primary pressure, which isoften applied from a pump or a hydraulic accumulator as the pressuresource to a supply connection of the valve, into a constant, reducedsecondary pressure. In addition, the increase in the secondary pressureat the assignable utility connection of the regulating valve resultingfrom external and application-specific influences is prevented with anadditional pressure lease to an additional fluidic connection of thevalve, commonly in the form of a tank connection or return connection.The design as a seat-tight pressure-regulating valve ensures the sealingof the connection from the primary pressure side to the regulatingpressure side or from the regulating pressure side to theafore-mentioned tank connection or return connection of the valve. Inthis way, once a static regulating pressure has been obtained, anincrease in this pressure is prevented by means of the sealing relativeto the primary pressure side. The reduction in pressure by means of therelief function commences only once a maximum pressure level isexceeded. The seat-tight construction of a pressure-regulative valvediffers from the slide construction, in which the opening cross sectionsof the through-flow directions are obtained by means of the axialdisplacement of a valve piston in a valve body provided with radialbores.

One example of this type of pressure-regulating valve is presented in EP1 970 787 B1. This known pressure-regulating seat valve for hydraulicsystems, in particular for machine tool clamping devices, is providedwith a main seat arranged between a supply pressure connection and aregulating pressure connection in the form of a utility connection, towhich main seat an upstream spring-loaded main closure element isassigned which, for the purpose of setting the regulating pressure bymeans of the main seat, can be mechanically loaded by means of aregulating piston which, downstream of the seat, is loaded by means ofthe regulating pressure against a regulating spring. Because in theknown solution a discharge valve with a seat valve construction isarranged in a flow path between the regulating pressure connection and adischarge connection or tank connection, which discharge valve can bemechanically controlled to the discharge connection when the regulatingpressure set by means of the regulating spring is exceeded until suchtime as the regulating pressure is restored, and because the activationof both the discharge valve and of the main closure element can be setby means of the regulating spring, this means that a three-waypressure-regulating seat valve is realized, which requires only a singlesetting opportunity for the regulating pressure setting, namely, for thepreloading of the regulating spring. This is achieved in particular bymeans of the integration of the flow path to the discharge connectionand of the discharge valve with a seat valve construction into the flowpath, and with the single regulating spring which acts both for thedischarge valve and the main seat valve.

On the basis of this prior art, the invention addresses the problem ofproducing a functionally-reliable pressure-regulating valve in aninexpensive manner, which pressure-regulating valve, in addition to apressure reduction function, also realizes a pressure-limiting function,with the pressure difference between the respective reduced pressure andthe pressure-limiting opening pressure being minimized in order to thusensure an energy-saving pressure-regulating valve operation. Inparticular, a maximum regulating pressure variation is to be achieveddue to the pressure sensitivity of the connected consumer.

This problem is solved by means of a pressure-regulating valve havingthe features of Claim 1 in its entirety.

Because, in accordance with the characterizing portion of Claim 1, thecontrol part has a control rod with two control bodies which are kept ata distance from one another, one of which control bodies controls atleast one fluidic connection between the supply connection and theutility connection and the other control body controls at least onefluidic connection between the utility connection and the tankconnection, a 3-way pressure regulating valve is thus created which,with a functionally-reliable and inexpensive construction, expands apressure reduction function with which it is provided to also include apressure-limiting function. Both the pressure reduction function and thepressure-limiting function can be appropriately regulated by means of asingle regulating pressure spring. The pressure-regulating valveaccording to the invention is preferably used in hydraulic clamping ofmachine tools and, thanks to the additional pressure-limiting function,it ensures maintenance of the clamping pressure in the case of pressureincreases due to external influences.

Compared with the known comparable valve solutions, the valve accordingto the invention has the advantage that the so-called pressure offset orthe pressure difference between the respective reduced pressure and theassignable pressure-limiting opening pressure of the valve is minimal,which results in an energy-saving operation and in particular, hydraulicconsumers which are connected to the pressure-regulating valve, such asclamping pressure units in the case of machine tools, can be actuated inan unhindered and direct manner, which also represents a significantsafety enhancement. Because the valve construction according to theinvention is formed in a seat-tight manner, undesirable leaks duringvalve operation are avoided, and the respective workpiece isappropriately protected even when high clamping force is applied. Inthis way, leak losses cannot result in a corresponding clamping pressureloss in the hydraulic clamping of the machine tool.

Because, according to the invention, the control bodies of the controlpart which are respectively responsible for this are firmly connected toone another via a control rod and are kept at a distance from oneanother, both the above-mentioned pressure reduction function and thepressure-limiting function can be realized with only one control part inan installation space-saving manner, with the forced coupling of the twocontrol bodies via the control rod ensuring a fail-safe operation.

Due to the direct coupling by means of the single-piece control partbetween the pressure-regulating seat in the valve housing and thepressure-limiting seat, no additional idle stroke is required in thevalve piston via the control part with its control rod and the twocontrol bodies in order to activate the pressure-limiting function. Theabove-mentioned pressure difference between regulated pressure andlimited pressure in the sealing regulating position is minimal becauseno additional sealing force is required to overcome a certain idlestroke. However, in order to open the pressure-limiting function, theloss of the compressive force, which is transferred via the closingpiston from the primary pressure side, must be compensated for.

In a particularly advantageous manner, a change in the seat diameter ofthe valve piston makes it possible to change the pressure differenceuntil such time as the pressure-limiting function is activated.

The control part formed according to the invention with the control rodand the two control bodies which are kept at a distance from one anotherby means of the control rod thus create a double-action sealing elementand, due to the gimbal-type mounting of the two control bodies in theform of spherical caps in the respective seat geometries of theassignable valve seats on the valve housing and on the valve piston, atolerance insensitivity is produced with regard to form tolerance andpositional tolerance of the valve components which are to this extentconnected to one another. This ensures a high level of tightness for thepressure-reduction function and for the pressure-limiting function.

Furthermore, the gimbal mounting provided ensures that the criticalloading case of the piston-type closing part with its two control bodiesis reduced to pulsating compressive loads. This permits a reduction inthe rod diameter of the control rod in the region of the seatfeed-through in the valve housing and provides additional advantages inreducing the pressure losses in the case of unloaded through-flow of thepressure-regulating valve. It is also advantageous that the tankconnection, return connection or discharge connection of thepressure-limiting function is arranged above the valve piston at theside on the valve housing, in which the valve piston is guided in alongitudinally displaceable manner. This makes it possible to applyatmospheric pressure to the spring side of the valve piston and thus tothe spring chamber with the regulating pressure spring accommodatedtherein, so that to this extent the actual pressure-regulating functionis thus virtually independent of the pressure in the discharge line,return line or tank line. The pressure existing in the latter line acts,as a compressive force, against the valve piston on the surface of thepressure-limiting seat, which is arranged in the region of the freefront end of the valve piston, which in turn faces the control part.

The pressure-regulating valve according to the invention is explained indetail below with reference to an exemplary embodiment according to thedrawings in which, in schematic and not to scale depictions,

FIG. 1 shows a longitudinal section through the pressure-regulatingvalve according to the invention;

FIG. 2 shows, on a magnified scale (3:1), a picture segment identifiedwith the letter A in FIG. 1;

FIG. 3 shows a picture segment, which is likewise on a magnified scale(6:1) and which is identified with the letter B, of a valve detailaccording to the depiction of FIG. 2 and

FIG. 4 shows, in the form of noted measurements, the volumeflow-dependent pressure regulating function with quadrant change whichcan be realized with the pressure-regulating valve according to FIGS. 1to 3.

The pressure-regulating valve depicted in FIG. 1 has a valve piston 10,which is guided in a longitudinally displaceable manner in a valvehousing 12. The valve housing 12 has different connection points whichcan be separated from one another, such as a supply connection 14, autility connection 16 and a tank connection 18. The respectiveconnection points can consist of several individual bores, with thesupply connection 14 entering the valve housing 12 at the front end andboth the utility connection 16 and the tank connection 18 beingintroduced laterally in a radial direction into the valve housing 12, asdepicted in FIG. 1. The supply connection 14, which is also referred toas a “supply pressure connection” or “pump pressure connection” intechnical parlance, serves to deliver a supply pressure, for example apump pressure or a hydraulic accumulator pressure, to the inside of thevalve housing 12 of the pressure-regulating valve. The primary pressureside or primary pressure connection 14 are technical descriptions whichare also commonly used. The utility connection 16 leads to a hydraulicconsumer which is not depicted in detail, for example in the form of ahydraulic clamping cylinder of a clamping device in the case of amachine tool. For the utility connection 16, the terms “secondaryconnection” or “secondary pressure side” are also used; the terms“regulating pressure side” or “consumer connection” are also common. Theterm tank connection 18 is also commonly described as a “returnconnection or discharge connection” in technical parlance. Theabove-mentioned terms are to this extent categorized and reference ismade to them to this extent below.

A control part 20 serves to actuate said connections or connectionpoints, which control part is depicted magnified in FIGS. 2 and 3 andwhich can close in a seat-tight manner. The control part 20 can beactuated in such a way that, in the case of a fluidic connection fromthe supply connection 14 to the utility connection 16, a pressurereduction function is realized, and in the case of a fluidic connectionfrom the utility connection 16 to the tank connection 18, apressure-limiting function is realized, which functions combined permita pressure-regulating function.

As is shown in particular in FIG. 3, the control part 20 has a controlrod 22 with two control bodies 24, 26 kept at a distance from oneanother, one 24 of which control bodies controls at least the fluidicconnection between the supply connection 14 and the utility connection16 and the other control body 26 controls at least the fluidicconnection between the utility connection 16 and the tank connection 18.The one control body 24 of the control part 20 can be brought intoseat-tight contact with a valve seat 28 of the valve housing 12, whichvalve seat is penetrated by the control rod 22, with the other controlbody 26 of the control part 20 being able to be brought into seat-tightcontact with a valve seat 30 of the valve piston 10. According to thedepictions of FIGS. 1 to 3, the second control body 26 is in itsright-hand stop position and thus arranged in a sealing manner on itsassigned second valve seat 30 in the valve piston 10. While the firstvalve seat 28 is designed with a spherical shape and conically tapered,the second valve seat 30 has a comparable conical taper with angularsurfaces which extend straight.

The control rod 22 penetrates, at a radial distance, a transversepartition wall 32 in the valve housing 12 via a penetration point 34which opens into the first valve seat 28 at its left-hand end whenviewed in the direction of viewing of FIG. 3, with the broadest diameterpoint of said first valve seat being flush with the left-hand front wallof the partition wall 32 of the valve piston 10. The diameter of thepenetration point 34 is in any case selected such that, when the entirevalve is assembled, the second control body 26 can also pass throughthis penetration point 34 in order to subsequently cooperate with thevalve piston 10 when the valve has been fully assembled. Furthermore,the partition wall 32 divides the valve housing into two fluid chambers36, 38, the one 36 of which has the supply connection 14 and the otherfluid chamber 38 having the utility connection 16. Depending on therespective displacement position of the control part 20 and the valvepiston 10, the volumes of the respective fluid chambers 36, 38 can varywithin predefinable limits.

The one control body 24 is supported at its left-hand end by means of astep 40 on an energy store in the form of a pressure spring 42, which ispenetrated by the fluid supply at the supply connection 14 and thespring stiffness of which is significantly less than the springstiffness of a regulating pressure spring 44, which permanently appliespressure to the valve piston 10 in each of its regulating positions andwhich likewise constitutes an energy store.

As can be seen in particular from the detail drawing according to FIG.2, the valve piston 10 has an internal ducting 46 with a longitudinalbore 48 and a transverse bore 50. The longitudinal bore 48 opens intothe second valve seat 30 by means of its one free end, and by means ofits other free end it opens into the transverse bore 50, which in turnopens at its ends in the region of the bores for the tank connection 18.The axial length of the control part 20 and the valve piston 10 isdimensioned such that, in any case when viewed in the viewing directionof FIGS. 2 and 3, in the left-most displacement position of the valvepiston 10, the control part 24 arrives, by means of its step, at acorresponding stop location, and in this stop position too, at least thetransverse bore 50 is still partially in a fluid-conducting overlap withthe tank connection 18 in the valve housing 12. Said internal ducting 46in the valve piston 10 with the longitudinal bore 48 and the transversebore 50 permits at least a fluid-conducting connection between theutility connection 16 and the tank connection 18 as soon as the onecontrol body 26 of the control part 20 lifts out of its assigned valveseat 30 in the valve piston 10.

The two control bodies 24, 26 each have spherical shaped body sectionsin the form of partial spherical caps and in FIG. 3 the sealing linesfor the two control bodies 24, 26 are represented with dashed lines andidentified with the reference numerals 52 and 54. It can also be seen,in particular from FIG. 2, that the one control body 26 of the controlpart 20 which is assigned to the valve seat 30 on the valve piston 10 issmaller in diameter relative to its above-mentioned circumferentialsealing line 52, preferably approximately ⅓ to a half smaller,particularly preferably precisely half as small, than the control body24 that faces the supply connection 14 with its diameter related to itssealing line 54. The above-described arrangement in any case results ina seat-tight construction in that there is always one of the two controlbodies 24, 26 contacting on its assigned valve seat 28, 30 or, ifappropriate, both control bodies 24, 26, depending on the respectivedisplacement position of the valve piston 10. There is also thepossibility that both control bodies 24, 26 are distanced from theirrespective assigned valve seat 28, 30 if this is required for theregulating tasks of the pressure-regulating valve.

The valve housing 10 has, in the region of the supply connection 14 andconnected thereto in a fluid-conducting manner, a recess in the form ofthe first fluid chamber 36, into which a holding device 56 is insertedfor receiving the pressure spring 42, on which the one control body 24of the control part 20 is supported. The holding device 56 is formed asa receiving pot and is inserted via connecting bars (not depicted) intothe fluid chamber 36 of the valve housing 12 in such a way that a radialdistance is formed between the inner wall of the fluid chamber 36 andthe outer wall of the holding device 56 which permits the entry ofpressurized fluid in the direction of the valve piston 10. Furthermore,the holding device 56 has on its bottom side a through hole 58, whichopens into a channel 60, which fully penetrates the holding device 56viewed in the longitudinal direction. In the region of the dome-likebroadening of the control body 24, this channel 60 is likewisecorrespondingly broadened and to this extent forms a cavity 62 for thepurpose of receiving the control body 24.

If the valve piston 10 is, in accordance with the depiction of FIG. 2,in its left-hand end position, said valve piston abuts, by means of afrontal, step-like broadening, an internal wall shoulder of the valvehousing 12. This step serves as a stroke stop for the valve piston 10.The necessary sealing is realized by means of standard soft sealing.

The above-mentioned regulating pressure spring 44 for the valve piston10 is guided, according to the depiction of FIG. 1, in a spring chamber64, which is surrounded by parts 66 of the valve housing 12 andpressurized with ambient pressure. The pressure spring 44 is supportedby means of each of its two free ends on an assigned cap guide 68, 70.The spring force of the pressure spring 44 can be set by means of astandard setting device 72, which acts by means of a ball guide on thetop cap guide 68. The bottom cap guide 70 is in turn in a functionalconnection with an actuation tappet 74 via a ball bearing, whichactuation tappet penetrates a connection piece 76 as an additional partof the valve housing 12. The valve housing part 66 is dovetailed at theends with wall parts of the setting device 72 and with the connectionpiece 76. A pressure equalizing channel 78 is arranged in the connectionpiece 76 which conveys the ambient pressure or atmospheric pressure tothe inside of the spring chamber 64. At the location where, viewed inthe viewing direction of FIG. 1, the bottom end of the actuation tappet74 emerges from the connection piece 76, the connection piece 76 has athread support for the screwing of the valve housing part 12.Furthermore, to achieve a rigid connection between the valve housing 12and the connection piece 76, the bottom free end of the connection piece76 is flanged in the direction of the outer wall of the valve housing12.

As can also be seen from FIG. 2, the actuation tappet 74 has a stop 80on its side facing the valve piston 10 for the housing parts in the formof the connection piece 76, which stop limits the free travel of thevalve piston 10 in the direction of its regulating pressure spring 44.Furthermore, the entire pressure-regulating valve, including its guidesystems and sealing systems, which will not be described in furtherdetail here, is designed using the so-called cartridge construction,which makes it possible to insert the pressure-regulating valve into anassignable valve block (not depicted) of a complete hydraulic system inan evident manner.

The regulating function of the pressure-regulating valve according tothe invention can be graphically represented with the aid of the diagramof FIG. 4 in two quadrants I and II. The noted measurements according toFIG. 4 are merely an exemplary representation which is intended toillustrate the ratios in the quadrant operation to be regulated. Theordinate of the diagram of FIG. 4 gives the secondary pressure in bar.The abscissa gives the volume flow in l/min. The transverse linesidentified with 25, 50, 100, 150 and 200 represent pressure stages inbar.

The first quadrant I presents the regulated, in particular reducedpressure in a defined valve setting of the pressure-regulating valveaccording to the invention dependent on the volume flow. Upon transitioninto the second quadrant II, the delivery volume from the primary side14 towards the secondary side 16 drops to zero. The closing operation ofthe regulating element which is responsible for this drop is realizedwith the seat-tight closing element 20 with the cap-shaped controlbodies 24, 26. This ensures that, once the regulated pressure and thezero-volume flow intake are achieved at the secondary connection 16, nofluid can flow from the primary side 14 to the secondary side 16 andproduce an undesirable pressure increase. If the pressure increases witha closed regulating element, the pressure-limiting function to the tankconnection or discharge connection 18 opens in the second quadrant II.This pressure-limiting function also operates using a specified volumeflow range.

This function has applications for example in hydraulic clamping ofmachine tools. The supply pressure of a hydraulic system is reduced tothe desired clamping pressure, which is responsible for realizing theclamping of a workpiece by means of hydraulic cylinders. When thedesired preloading of the cylinder is achieved, the control part 30 inthe form of the first control body 24 seals the primary pressure side 14(supply pressure side) relative to the secondary pressure side (clampingpressure side) 16. During the machining of the thus firmly clampedworkpiece, temperature increases or machining forces can result inpressure increases on the secondary pressure side 16. This pressureincrease is dissipated without an additional valve via thepressure-limiting function in the pressure-regulating valve according tothe invention. The important thing here is that the regulated primarypressure at the supply connection 14 and the opening pressure of thepressure-limiting function can both be set by means of a spring, in thiscase the regulating pressure spring 44, which spring acts upon theregulating element in the form of the valve piston 10 and pushes againstthe primary pressure. The goal here is to maintain as low as possiblethe pressure difference between regulated pressure at zero-volume flowand the opening pressure of the pressure-limiting function, irrespectiveof the setting pressure of the valve according to the invention, whichis represented in a schematic manner in FIG. 4 by the so-called pressureoffset ranges 82 for the individual pressure stages 25 to 200 bar at thezero-volume flow line.

By comparison with the prior art, the pressure-regulating valve solutionaccording to the invention thus provides a valve in which the shownpressure offset range 82 between reduced pressure and pressure-limitingopening pressure is minimal, and this constitutes a significant safetyfeature when using the pressure-regulating valve according to theinvention, in particular in the context of hydraulic clamping of machinetools. The advantages of the valve thus include the energy efficiencywhen used in hydraulic clamping of machine tools due to the seat-tightconstruction by comparison with pressure-regulating valves with a slideconstruction, in particular no losses resulting from long-lasting leakflow occur in the solution according to the invention.

1. A pressure-regulating valve having a valve piston (10) which issubjected to the action of an energy store and which is guided in alongitudinally displaceable manner in a valve housing (12), which valvehousing has connection points such as a supply connection (14), autility connection (16) and a tank connection (18), which connectionscan be actuated, by means of a control part (20) which closes in aseat-tight manner, such that, in the case of a fluidic connection fromthe supply connection to the utility connection, a pressure reductionfunction is realized, and in the case of a fluidic connection from theutility connection to the tank connection, a pressure-limiting functionis realized, characterized in that the control part (20) has a controlrod (22) with two control bodies (24, 26) which are kept at a distancefrom one another, the one (24) of which control bodies controls at leastthe fluidic connection between the supply connection (14) and theutility connection (16) and the other control body (26) controls atleast the fluidic connection between the utility connection (16) and thetank connection (18).
 2. The pressure-regulating valve according toclaim 1, characterized in that the one control body (24) of the controlpart (20) can be brought into seat-tight contact with a valve seat (28)of the valve housing (12) which valve seat is penetrated by the controlrod (22), and in that the other control body (26) of the control part(20) can be brought into seat-tight contact with a valve seat (30) ofthe valve piston (10).
 3. The pressure-regulating valve according toclaim 1, characterized in that the control rod (22) penetrates, at aradial distance, a partition wall (32) of the valve housing (12), whichhas the one valve seat (28), and in that the partition wall (32) dividesthe valve housing (12) into two fluid chambers (36, 38), the one (36) ofwhich has the supply connection (14) and the other fluid chamber (38)has the utility connection (16).
 4. The pressure-regulating valveaccording to claim 1, characterized in that the one control body (24) issupported on an energy store, in particular in the form of a pressurespring (42), which is penetrated by the fluid supply and the springstiffness of which is much lower than the spring stiffness of aregulating pressure spring (44) which, by means of its spring force,permanently applies pressure to the valve piston (10) in each of itsregulating positions.
 5. The pressure-regulating valve according toclaim 1, characterized in that the valve piston (10) has an internalducting (46), which permits at least a fluid-conducting connectionbetween the utility connection (16) and the tank connection (18) as soonas the one control body (26) of the control part (20) lifts out of itsvalve seat (30) in the valve piston (10).
 6. The pressure-regulatingvalve according to claim 1, characterized in that the one control body(26) of the control part (20) assigned to the valve seat (30) on thevalve piston (10) is smaller in diameter relative to its circumferentialsealing line (54), preferably approximately one third to a half smaller,than the control body (24) that faces the supply connection (14) withits diameter related to its sealing line
 54. 7. The pressure-regulatingvalve according to claim 1, characterized in that the valve housing (10)has, in the region of the supply connection (14) and connected theretoin a fluid-conducting manner, a recess (36), into which a holding device(56) is inserted for receiving that pressure spring (42) on the one freeend of which the one control body (24) of the control part (20) issupported, which can be at least partially received in a cavity (62) ofthe holding device (56).
 8. The pressure-regulating valve according toclaim 1, characterized in that the regulating pressure spring (44) forthe valve piston (10) is guided in a spring chamber (64) which,surrounded by parts (66) of the valve housing (12), is pressurized withambient pressure, and in that the regulating pressure spring (44) actsupon one end of an actuation tappet (74), the other end of which restsloosely on the valve piston (10), and in that the actuation tappet (74)is guided in a longitudinally displaceable manner in a connection piece(76) as an additional part of the valve housing (12).
 9. Thepressure-regulating valve according to claim 1, characterized in thatthe actuation tappet (74), on its side facing the valve piston (10),forms with the housing parts (76), inside which it is guided in alongitudinally displaceable manner, a stop (80), which limits the freetravel of the valve piston (10) in the direction of its regulatingpressure spring (44).
 10. The pressure-regulating valve according toclaim 1, characterized in that it is designed using the cartridgeconstruction for insertion into an assignable valve block of a completehydraulic system.